Improved magnetocaloric effect in magnetron sputtered Ni–Mn–Sb–Al ferromagnetic shape memory alloy thin films

• The grain size and Ravg have been decreased with the addition of Al content.
• Martensitic transformation temperature TM decreases with increasing Al content.
• The highest value of ΔS = 15.2 mJ/cm3-K is observed in Ni50Mn36.3Sb10.4Al3.3.
• Higher H = 12.6 ± 2.2 GPa and E = 280 ± 2.3 GPa are found in Ni49.7Mn36.4Sb8.3Al5.6.

The present study systematically explored the effect of Aluminium (Al) addition on the martensitic phase transformation, magnetocaloric effect (MCE) and mechanical properties in Ni–Mn–Sb ferromagnetic shape memory alloy (FSMA) thin films. From the isothermal magnetization (M−H) curves, a large entropy change ΔS = 15.2 mJ/cm3 K at 272 K was found in Ni50Mn36.3Sb10.4Al3.3 thin film. The refrigeration capacity (RC) was also calculated for all the thin films in an applied magnetic field of 2 T. Further, the room temperature nanoindentation measurements have performed for all these thin films and it reveals the higher values of hardness and elastic modulus of about 12.6 ± 2.2 and 280 ± 2.3 GPa in Ni49.7Mn36.4Sb8.3Al5.6 thin film. Hence, the appropriate addition of Al significantly improves the mechanical properties as well as MCE of Ni–Mn–Sb thin films. These findings indicate Ni–Mn–Sb–Al thin films are potential candidates for micro-length scale magnetic refrigeration applications.